I was in Hong Kong last week and one of the things that amazed me is that the "city centre" (Kowloon and Hong Kong Island) is fairly small and has lots of green spaces. Hong Kong Island has a density of 16,000/km2 but the actual urban area is around 20% of the island [0]. Housing really is densely packed (I haven't ever seen people queuing for an elevator to get into their apartment building before), but I think I'd much prefer that to living in an urban sprawl where I have to drive 30 minutes to see something green.

[0] https://www.google.com/maps/place/Hong+Kong+Island,+Hong+Kon...